1. Field of the Invention
This invention relates to a weight tape for modifying an unbalance of a tire wheel, and in particular for modifying an unbalance of the weight of a tire wheel which is a combination of a wheel and a tire.
2. Description of the Prior Art
Conventionally, there are provided weights for modifying an unbalance of a tire wheel, which comprise a plurality of weight pieces each having a certain amount of weight and substantially separated from each other on a separable sheet.
However, the unbalance of weight of the tire wheel to be modified is often inconsistent with the weight of the weight piece. Therefore, in fact, it is often necessary to modify the unbalance without using this basic weight as it is. In this case, since the weight piece is cut by eye measurement to have the necessary weight, the weight of the cut weight piece tends to be inexact and some unbalance still remains, and consequently the efficiency of the modification to the tire wheel to balance it is low.
In addition, the conventional weight piece for modification is made to have a shape, under a prerequisite that the weight piece having a weight close to the weight needed to modify the unbalance is selected for use and then the weight is adhered so that the weight of the weight piece is narrowly concentrated to the location on the wheel required to modify the unbalance.
FIG. 7 of the accompanying drawings shows an example of a conventional weight piece 20 which is thick at a center portion and has an adhesive portion 22 adhered on an inner surface of a rim of a wheel. This shape is used for a weight having a relatively large weight and fits the shape of the inner surface of the rim so that the weight is concentrates to the location to be modified. FIG. 8 of the drawings shows another example of a conventional weight piece 20 having an elliptical shape which also has an adhesive portion 22 and is attached on the inner surface of the rim. FIG. 9 shows another example of a conventional weight piece 20 comprising a cylindrical shape portion and a clip 24, which is attached by driving the clip between a flange portion of the rim and the tire.
In these cases wherein the concentrated modification is achieved, a slight vibration similar to a vibration caused by remaining unbalance occurs during actual driving and comfort and stability of driving are degraded.
It is possible to adopt a system utilizing many kinds of weight pieces having different basic weights, wherein a weight piece having a smaller basic weight, which is less than required when one basic weight is used, is selected and both weight pieces are adhered. However, since demanding high-speed driving performance for vehicles is increasingly required and there is a need to remove vibration during high-speed driving, and precise modification within a weight difference of one gram or less is required. As a result, in this system, small weight pieces having a weight of one gram or less have to be used. In this case, it is difficult to prevent dust from adhering to the adhesive portion of the weight pieces and it is also difficult to handle them and maintain their shape. Further, tight adhesion to the wheel is disturbed and there is a possibility of removal during driving and of thus generating wheel vibration.
Furthermore, since tire wheels are often required to be fashionable such as the preference for aluminium wheels, it is increasingly required that the weight for modification is adhered to the radially inner surface of a rim (which is called "inner surface of a rim" hereinafter) at an axially inside portion of the wheel on viewing from a vehicle on which the tire wheel is mounted in order not to expose the weight piece. The rim is composed of a multiple curved surface and a disc portion of the wheel also has many kinds of concave and convex portions, and therefore a weight piece having conventional size and shape often cannot be adhered to the point which should be modified. In this case, the weight piece has to be adhered at a position nearest the exact position which should be modified not to protrude out of the wheel, and consequently the effect of modification of unbalance is decreased by this difference of position.
For the purpose that a weight piece having a certain weight is adhered so that the weight of the weight piece exactly concentrates at the location to be modified, it is possible to make its thickness larger than its length. However, the weight piece becomes lump-like and causes problems such as contacting braking apparatus. Further, in the case of this thick weight piece, it is difficult to cut other than along a cutting line which is provided for the purpose of easy cutting and formed during the producing process of the weight piece, and the cutting causes distortion of the weight piece which prevents it from secure adhesion, resulting in dropping or scattering during driving or generating of vibration.
An object of this invention is to overcome the above mentioned problem, that is to provide a weight tape for modifying unbalance which can modify unbalance within a small weight difference of one gram or less and contribute to eliminating vibration precisely during high speed driving.